“That means producing billions of doses of it, which, in itself, is a huge challenge in terms of manufacturing logistics. And despite the efforts, it is still not even certain that developing a COVID-19 vaccine is possible.”

Prof Piot criticised anti-vaxxers, saying: “Today there’s also the paradox that some people who owe their lives to vaccines no longer want their children to be vaccinated.

“That could become a problem if we want to roll out a vaccine against the coronavirus, because if too many people refuse to join, we will never get the pandemic under control.”

He said he hoped the coronavirus pandemic can help ease political tensions, citing how polio vaccination campaigns have led to truces between countries.

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He said he hoped the WHO could be “reformed to make it less bureaucratic”, saying it too often resembles a “political battleground”.

According to Johns Hopkins University, the US is the worst-hit country by coronavirus, with more than 79,500 deaths, followed by the UK with more than 31,900 and Italy with more than 30,500.

On Sunday, British prime minister Boris Johnson announced a range of new measures to ease the UK out of its COVID-19 lockdown.